Heat exchanger construction



:Jan. 13, 1959 R. J. GARLAND 2,868,515

HEAT EXCHANGER CONSTRUCTION Filed Nov. 25, 1955 INVENTOR.

United States Patent HEAT EXCHANGER co sTRUcTIoN Robert J. Garland, De Witt, N.. 5;, assignor to Carrier Corporation, Syracuse, N. Y., a corporation of Bellaware Application November 25, 1955,Serial No. 548,891

1 Claim. (Cl. 257-26210) This invention relates to a novel heat exchanger of the serpentine coil type, and more particularly to an arrangement, of helically finned tubing serving to provide a maximum rate of heat exchange between any fiuids flowing in said tubing, and the fluids surrounding the same.

It is customary to provide helically extending fins on fluid conduits or tubing to increase the efiective surface area of the conduits or tubing. Such helical fins may be rolled or wrapped on the tubing in any manner, for example, by means of the finning machine disclosed in my copending application, Serial No. 498,162, filed March 31, 1955, entitled Finning Machines.

I have found, however, that the provision of a helical fin on the tubing, though increasing the effective surface area of said tubing, interferes with the formation of small return bends when the finned tubing is employed for fabrication of conventional heat exchangers such as serpentine coils. In employing finned tubing in the construction of immersion heaters, evaporator coils, condenser coils and the like, it is generally found most efficient to provide a maximum amount of tubing within any given volume in which the heat exchange is to take place. In hte manufacture of serpentine coils, the pres ence of the helical fins on the tubing interferes with the formation of small return bends, for, at the points of curvature, the fins interfere with each other. Ordinarily, the fins are stripped from the portion of tubing which will be used to form the return bend thus eliminating the above noted interference. As is apparent the heat transfer coefficients of the coil at the stripped return bends are considerably diminished. It is in fact found that the effectiveness of heat transfer is to such an extent nullified by removal of the fins, that the bent portion is often arranged outside the enclosure between which heat transfer is to take place. This of course results in a waste of tubing, and increases fabrication costs of the heat exchanger housing.

The chief object of this invention is to provide an improved heat exchanger of the sepentine coil type.

An object of this invention is to provide a novel finned tubing construction.

A further object of this invention is to provide an improved finned serpentine coil fabricated of helically finned tubing which will permit fabrication of return bends in the tubing to form the coil.

A still further object is to provide means for increas ing the utility of all portions of helically finned tubing employed in a serpentine coil.

These and other objects of this invention which will become apparent from this disclosure, and the accompanying claim, are achieved by provision of fins of reduced diameter at that portion of the tubing which it is desired to bend. Preferably, these fins of reduced diameter are provided at the time fins are wrapped or rolled about the tubing.

The specific structural arrangement of this tube, and its method of formation will be made most manifest and particularly pointed out in conjunction with the accompanying drawings wherein:

Figure l is a view in elevation of a portion of a length of helically finned tubing, illustrating the section of reduced fin diameter to be employed to form a return bend of a serpentine coil; and

Figure 2 is a fragmentary view in elevation of a serpentine coil heat exchanger embodying the tubing of Figure 1 and illustrating a return bend formed therefrom.

Referring now more particularly to the drawings, like numerals in the various figures will be taken to designate like parts.

As best seen in Figure 1, tubing 10 is provided with fins 11, extending outwardly from the sidewalls oflsaid tubing. Preferably, the fins are rolled or wrapped on the tube by the fining machine disclosed in my copending application referred to above in which a ribbon of desired width and thickness is passed between forming rolls which wrap or roll the ribbon into a helical fin extending about the tube. The user of finned tubing will conventionallly have available lengths of finned tubing of uniform diameter. These lengths are thereafter employed in the fabrication of any heat transfer equipment, and as is apparent the need often arises to provide bends at various points in the tubing employed, so as to facilitate positioning of the tubing to cover any given area.

Wherea return bend is to be formed in the tubing, with adjacent runs of tubing lying as close as possible to each other, it is found that the fins provided about the portion of the tubing to be bent interfere with each other, preventing the formation of a relatively small radius bend. Thus, in the formation of a bend, as illustrated in Figure 2, it is found that this relatively small radius return bend may readily be formed, if the fins extending outwardly from the tubing along the portions thereof to be bent are previously reduced in size so as to decrease the outer diameter of the finned tube.

This portion $12, to be bent has its fins reduced in diameter as seen in the drawings. Preferably, a slitting device is added to the finning machine to slit desired sections from the ribbon being supplied to the finning machine thus forming sections of ribbon of less width. When the ribbon is rolled about the tube, the sections of the fins formed by the ribbon of less width are less in diameter than the major portion of the fins. These sections are selected carefully and so spaced that the return bends of the serpentine coil to be made from the tubing are fabricated from such sections.

The fragmentary portion of the serpentine coil shown in Figure 2 comprises two linear runs 13 of tubing 10 having fins lit, with the linear runs 13 interconnected by an arcuate run of tubing 14 having fins of reduced diameter which forms a return bend section of the coil.

In employing the above disclosed finned tubing construction in accordance with a prefered mode of applying the teachings of this invention to the formation of serpentine coil heat exchangers, the length of tubing formed as described above is bent into serpentine form by employing conventional tube bending techniques involving the use of forming rolls, or the like. The portions of reduced fin diameter are employed as the return bends of the coil so formed.

It is thus seen that a heat exchange arrangement employing finned tubing has been provided which permits provision of a maximum amount of tubing in any given volume in which heat exchange is to be effected. This will provide a maximum efiective surface area for any given volume. It is not necessary to strip the fins from those portions of the tube forming return. bends to permit adjacent runs of tubing to be placed close together while the amount of heat exchange surface available at the return bends is enhanced. The return bends of the I? serpentine coil carry fins to increase the elfective heat exchange surface even though those fins do not possess a diameter as great as the diameter of the fins carried by the horizontal or vertical runs of the coil.

The above disclosure has been given by way of illustration and elucidation, and not by way of limitation, and it is desired to protect all embodiments of the hereindisclosed inventive concept Within the scope of the appended claim.

I claim:

A heat exchanger coil construction comprising a con tinuous run of tubing in the form of a serpentine coil, said tubing having helical fins thereon comprising a ribbon of desired height and thickness having spaced portions thereof of less height than the body of the ribbon, the fins extending a uniform distance from the tubing along the length thereof except at the arcuate portions References Cited in the file of this patent UNITED STATES PATENTS 1,710,811 Dewald Apr. 30, 1929 1,760,039 Bundy May 27, 1930 1,909,005 Paugh May 16, 1933 2,225,773 Dufault Dec. 24, 1940 2,337,490 Penner Dec. 21, 1943 FOREIGN PATENTS 5971 64 France Nov. 21, 1925 

